Other than Boku no Pico...Bludgeoning Angel Dokuro-Chan is pretty messed up too but hell that's the most hilarious anime I ever watched other than bobobo-bo bo-bobo.

It really was. Enzai was screwed up, too- just thought it was going to be a regular shounen-ai show. I was completely wrong...*shivers*.
Dokuro-chan was pretty disturbing although I agree it was hilarious

Paranoia Agent is definitely my favorite anime, and it is a show that remains twisted throughout. Given that the most cheerful episode is about

Spoiler Alert! Click to show or hide

3 people, including a young girl, trying to commit suicide,

I think that this show is definitely pretty twisted. I feel like it is more effective than some other shows, like Future Diary and Higurashi, because it isn't about kids, and is really more about ordinary people going crazy.
Basically, I really recommend watching Paranoia Agent, especially if you like twisted psychological anime.

Yes! And I'm super excited for the upcoming live action adaptation for HBO directed by Guillermo del Toro. I plan to use it as a tool to demonstrate the validity of complex and mature story telling in anime as a medium to the non believers. Bwhahaha!